This is the cheapest I have seen the Nest Protect since the JB Pricing Error https://www.ozbargain.com.au/node/357593
Battery - https://www.ebay.com.au/itm/NEW-Nest-3696923-Protect-Smoke-A…
Wired - https://www.ebay.com.au/itm/NEW-Nest-3696924-Protect-Smoke-A…
Updated title to mention CO
https://www.jbhifi.com.au/nest/nest-protect-smoke-alarm-batt… same model sold by JB for $149
@Mobe1969: Yes they do - as I had my Sparky call up Master Electricians and they confirmed the wired ones DO MEET the regulations. Also confirm that they have a battery backup in them too.